Pierce the eggplant 4 or 5 times with the tip of a paring knife. Microwave on High for 6 to 8 minutes until softened, then place on a plate and allow to cool to room temperature.
Peel off the skin and stem, discard. Roughly chop the eggplant and place into a blender along with the tahini, lemon juice, garlic and olive oil. Puree until smooth, adding water if needed to make a thick paste; season to taste with salt.